Gas distribution plate for chemical vapor deposition systems and methods of using same

ABSTRACT

In one aspect, a system for depositing a layer on a substrate is provided. The system includes a processing chamber, a gas injecting port, a gas distribution plate, and a plug. The gas injecting port is disposed upstream from the processing chamber. The gas distribution plate is disposed between the gas injecting port and the processing chamber, and includes an elongate planar body and an array of holes therein. The plug is sized to be received within one of the holes, and includes an orifice therethrough for permitting the passage of gas. The plug is capable of being removably secured to the gas distribution plate within one of the holes.

FIELD

The field relates generally to the use of chemical vapor depositionsystems in processing semiconductor wafers and, more specifically, togas manifolds and to methods for controlling the uniformity of gas flowwithin a chemical vapor deposition process chamber.

BACKGROUND

In chemical vapor deposition (CVD) processes, including epitaxial growthprocesses, uniformity in the thickness of a deposited film on asubstrate is dependent on, among other factors, uniformity in the flowdistribution of gasses within the process chamber. As the requirementsfor uniformity in film thickness become more stringent, the desire formore uniform flow rate distribution of gasses in the process chamberincreases.

In conventional CVD devices, a source gas is introduced into the processchamber through a gas manifold. The gas manifolds of conventional CVDdevices do not provide adequate control of the gas flow distributionacross the substrate surface in the processing chamber.

For example, baffle plates used in conventional gas manifolds have fixedhole sizes that cannot be adjusted without replacing the entire baffleplate. Thus, conventional baffle plates do not permit selectiveadjustment of the gas flow distribution across the substrate surface,which may be needed when changing process parameters such as the flowrate of the process gas.

Additionally, injection port liners and inject inserts used inconventional gas manifolds do not provide sufficient uniformity in thegas flow distribution across the substrate surface. For example, someinjection port liners may include multiple flow zones having differentprocess gases or gas flow rates which feed into a single channel definedwithin the inject insert. As a result of the “crosstalk” between themultiple flow zones feeding into a single inject insert channel,attempts to tune the gas flow distribution within the processing chamberby varying the type of gas or gas flow rate in the different flow zoneshave unpredictable tuning results.

Additionally, in operation, localized zones of cyclically flowing gas,known as “recirculation cells,” often form within the channels of injectinserts used in conventional gas manifolds. Recirculation cells resultin degraded uniformity of the gas flow distribution within theprocessing chamber, which results in strong variations inepitaxially-grown films.

The foregoing problems attributable to conventional gas manifolds areamplified when the flow rate of the process gas is increased, which isdesirable to increase the throughput of the CVD device.

Accordingly, a need exists for a gas manifold capable of delivering amore uniform flow rate distribution across the surface of a substratewithin the processing chamber.

This Background section is intended to introduce the reader to variousaspects of art that may be related to various aspects of the presentdisclosure, which are described and/or claimed below. This discussion isbelieved to be helpful in providing the reader with backgroundinformation to facilitate a better understanding of the various aspectsof the present disclosure. Accordingly, it should be understood thatthese statements are to be read in this light, and not as admissions ofprior art.

BRIEF SUMMARY

In one aspect, a system for depositing a layer on a substrate isprovided. The system includes a processing chamber, a gas injectingport, a gas distribution plate, and a plug. The gas injecting port isdisposed upstream from the processing chamber. The gas distributionplate is disposed between the gas injecting port and the processingchamber, and includes an elongate planar body and an array of holestherein. The plug is sized to be received within one of the holes, andincludes an orifice therethrough for permitting the passage of gas. Theplug is capable of being removably secured to the gas distribution platewithin one of the holes.

In another aspect, a method of depositing an epitaxial layer on asilicon wafer is described. The silicon wafer has a diameter, and isdisposed within a processing chamber within a deposition system. Themethod includes the steps of introducing a process gas into the systemfrom a gas injecting port, flowing the process gas through a gasdistribution plate in fluid communication with the gas injecting portand the processing chamber, the gas distribution plate including aninner array of holes and an outer array of holes, and controlling thegas flow distribution across the substrate surface. The controlling stepincludes selecting at least one orifice-containing plug to be securedwithin a hole in the gas distribution plate, and securing the selectedplug within the hole.

In yet another aspect, a system for depositing a layer on a substrate isprovided. The system includes a processing chamber, a gas injecting portfor introducing gas into the system, a gas distribution plate disposedbetween the gas injecting port and the processing chamber, the gasdistribution plate including holes therein, and an inject insert linerassembly received within the system adjacent to the gas distributionplate and upstream from the processing chamber. The inject insert linerassembly defines gas flow channels therein extending along a lengthwisedirection of the system, wherein each channel includes an inlet and anoutlet, and at least one channel is tapered along the lengthwisedirection of the system in at least one of a vertical or horizontaldirection. The inject insert liner assembly has the same number of gasflow channels as the number of holes in the gas distribution plate.

In yet another aspect, a system for depositing a layer on a substrate isprovided. The system includes a processing chamber, a gas injecting portfor introducing gas into the system, a gas distribution plate disposedbetween the gas injecting port and the processing chamber, the gasdistribution plate including holes therein, and an inject insert linerassembly received within the system adjacent to the gas distributionplate and upstream from the processing chamber. The inject insert linerassembly defines gas flow channels therein extending along a lengthwisedirection of the system. Each channel has an inlet adjacent to the gasdistribution plate and an outlet downstream from the inlet. Each channelis tapered along the lengthwise direction of the system in at least oneof a vertical or horizontal direction.

In yet another aspect, a method of depositing an epitaxial layer on awafer is described. The wafer has a diameter, and is disposed within aprocessing chamber within a deposition system. The deposition systemincludes a gas distribution plate in fluid communication with a gasinjecting port and the processing chamber. The method includes the stepsof introducing a process gas into the system from the gas injectingport, flowing the process gas through a flow channel extending along alengthwise direction of the system and being tapered along thelengthwise direction of the system in at least one of a vertical orhorizontal direction, wherein the flow channel is defined by an injectinsert liner assembly adjacent to the gas distribution plate, anddepositing an epitaxial layer on the wafer.

In yet another aspect, a method of depositing a layer on a silicon waferis described. The silicon wafer has a diameter and is disposed within aprocessing chamber within a deposition system. The deposition systemincludes a gas distribution plate in fluid communication with a gasinjecting port and the processing chamber. The method includes the stepsof introducing a process gas into the system from the gas injecting portat a flow rate, wherein the flow rate is at least about 15 standardliters per minute, and flowing the process gas through a flow channelextending along a lengthwise direction of the system and being taperedalong the lengthwise direction of the system in at least one of avertical or horizontal direction, wherein the flow channel is defined byan inject insert liner assembly adjacent to the gas distribution plate.

In yet another aspect, a method of depositing a layer on a substrate isdescribed. The substrate is disposed within a processing chamber withina deposition system. The method includes the steps of introducing aprocess gas into the system from a gas injecting port, flowing theprocess gas through a gas distribution plate in fluid communication withthe gas injecting port and the processing chamber, the gas distributionplate including an inner array of holes and an outer array of holes, andcontrolling the gas flow distribution across the substrate surface. Thecontrolling step includes selecting at least one orifice-containing plugto be secured within a hole in the gas distribution plate, and securingthe selected plug within the hole.

In yet another aspect, a method of depositing a layer on a substrate isdescribed. The substrate is disposed within a processing chamber withina deposition system. The deposition system includes a gas distributionplate in fluid communication with a gas injecting port and theprocessing chamber. The method includes the steps of introducing aprocess gas into the system from the gas injecting port, flowing theprocess gas through a flow channel extending along a lengthwisedirection of the system and being tapered along the lengthwise directionof the system in at least one of a vertical or horizontal direction, theflow channel being defined by an inject insert liner assembly adjacentto the gas distribution plate, and depositing a layer on the substrate.

Various refinements exist of the features noted in relation to theabove-mentioned aspects. Further features may also be incorporated inthe above-mentioned aspects as well. These refinements and additionalfeatures may exist individually or in any combination. For instance,various features discussed below in relation to any of the illustratedembodiments may be incorporated into any of the above-described aspects,alone or in any combination.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section of a chemical vapor deposition systemincluding a gas manifold of one embodiment of the present disclosure;

FIG. 2 is a perspective view of the chemical vapor deposition system ofFIG. 1, with certain components removed for illustration;

FIG. 3 is a perspective view of the gas manifold shown in FIGS. 1 and 2,including a baffle plate and an inject insert liner assembly of oneembodiment of the present disclosure;

FIG. 4 is a perspective view of the baffle plate shown in FIG. 3;

FIG. 5 is a perspective view of two plugs suitable for use with thebaffle plate shown in FIG. 4;

FIG. 6 is an alternative embodiment of the plugs shown in FIG. 5;

FIG. 7 is another alternative embodiment of the plugs shown in FIG. 5.

FIG. 8 is a perspective view of a baffle plate and plug combination ofone embodiment of the present disclosure;

FIG. 9 is an exploded front view of the baffle plate and plugcombination shown in FIG. 8;

FIG. 10 is an exploded top view of the baffle plate and plug combinationshown in FIG. 8;

FIGS. 11 and 12 are perspective views of the inject insert linerassembly shown in FIG. 3; and

FIGS. 13 and 14 are perspective views of an alternative embodiment ofthe inject insert liner assembly shown in FIGS. 11 and 12.

Like reference symbols used in the various drawings indicate likeelements.

DETAILED DESCRIPTION

A chemical vapor deposition (CVD) system is indicated generally at 100in FIG. 1. The illustrated system is a single substrate system, however,the system and methods disclosed herein for providing a more uniform gasflow distribution are suitable for use in other system designsincluding, for example, multiple substrate systems. One example of a CVDsystem suitable for use in accordance with the present disclosure is theApplied Materials EPI Centura 300.

The CVD system 100 includes a reaction or processing chamber 102 fordepositing and/or growing thin films on a substrate 104 (e.g., asemiconductor wafer), a gas injection port 106 disposed at one end ofthe processing chamber 102, and a gas discharge port 108 disposed at anopposite end of the processing chamber 102. A gas manifold 140 disposedbetween the gas injecting port 106 and the processing chamber 102 isused to direct incoming gas 110 into the processing chamber 102 enclosedby an upper window 112 and a lower window 114 through the gas injectionport 106. As shown in more detail in FIG. 2, the gas manifold 140includes an injector baffle or gas distribution plate 145 disposedbetween the gas injecting port 106 and the processing chamber 102, andan inject insert liner assembly 170 disposed adjacent to the baffleplate 145 and upstream from the processing chamber 102. In operation, anincoming process gas 110 flows through the gas manifold 140 and into thereaction chamber 102 through gas inlet 103. The gas 110 then flows overthe substrate surface 116 and reacts with the substrate surface 116, orprecursors disposed thereon, to deposit a film on the substrate surface116. The gas 110 then flows out of the reaction chamber 102 and throughthe gas discharge port 108.

The substrate 104 upon which the film is deposited is supported by asusceptor 120 within the reaction chamber 102. The susceptor 120 isconnected to a shaft 122 that is connected to a motor (not shown) of arotation mechanism (not shown) for rotation of the shaft 122, susceptor120 and substrate 104 about a vertical axis X of the CVD system 100. Theoutside edge 124 of the susceptor 120 and inside edge of a preheat ring126 (for heating the incoming gas 110 prior to contact with thesubstrate 104) are separated by a gap to allow rotation of the susceptor120. The substrate 104 is rotated to prevent an excess of material frombeing deposited on the wafer leading edge and provide a more uniformepitaxial layer.

Incoming gas 110 may be heated prior to contacting the substrate 104.Both the preheat ring 126 and the susceptor 120 are generally opaque toabsorb radiant heating light produced by high intensity radiant heatinglamps 128 that may be located above and below the reaction chamber 102.Equipment other than high intensity lamps 128 may be used to provideheat to the reaction chamber 102 such as, for example, resistanceheaters and inductive heaters. Maintaining the preheat ring 126 and thesusceptor 120 at a temperature above ambient allows the preheat ring 126and the susceptor 120 to transfer heat to the incoming gas 110 as thegas 110 passes over the preheat ring 126 and the susceptor 120. Thediameter of the substrate 104 may be less than the diameter of thesusceptor 120 to allow the susceptor 120 to heat incoming gas 110 beforeit contacts the substrate 104. The preheat ring 126 and susceptor 120may be constructed of opaque graphite coated with silicon carbide.

The upper and lower windows 112, 114 each comprise a generally annularbody made of a transparent material, such as quartz, to allow radiantheating light to pass into the reaction chamber 102 and onto the preheatring 126, the susceptor 120, and the wafer 104. The windows 112, 114 maybe planar, or, as shown in FIG. 1, the windows 112, 114 may have agenerally dome-shaped configuration. Alternatively, one or both of thewindows 112, 114 may have an inwardly concave configuration. The upperand lower windows 112, 114 are coupled to the upper and lower chamberwalls 130, 132 of the processing chamber 102, respectively.

The upper and lower chamber walls 130, 132 define the outer perimeter ofthe processing chamber 102, and abut the gas injection port 106 and thegas discharge port 108.

The CVD system 100 may include upper and lower liners 134, 136 disposedwithin the processing chamber to prevent reactions between the gas 110and the chamber walls 130, 132 (which are typically fabricated frommetallic materials, such as stainless steel). The liners 134, 136 may befabricated from suitably non-reactive materials, such as quartz.

Referring now to FIG. 2, wherein portions of the CVD system 100 havebeen removed for illustration, the gas manifold 140 includes an injectorbaffle or gas distribution plate 145 and an inject insert liner assembly170. The inject insert liner assembly 170 is configured to be receivedwithin the system 100 adjacent to the gas distribution plate 145 andupstream from the processing chamber 102. The inject insert linerassembly 170 may be a single or unitary insert, or it may be formed fromseparate inserts, including, for example, a first inject insert 170L anda second inject insert 170R, as shown in FIG. 3. In some embodiments,the first inject insert 170L and second inject insert 170R may each befurther divided into separate components, including upper halves 170La,170Ra and lower halves 170Lb, 170Rb, as shown in FIGS. 13-14. Themanifold 140 may also include an injection port liner 141, which may bedivided into two outer injection port liners 142, 143 and an innerinjection port liner 144. The injection port liner 141 is in fluidcommunication with the gas injection port 106. In some embodiments, thegas injection port 106 may be divided into two or more separate processlines (not shown), and the outer injection port liners 142, 143 may bein fluid communication with a source of process gas through a firstprocess line (not shown) and the inner injection port liner 144 may bein fluid communication with a source of process gas through a secondprocess line (not shown) so as to create two flow zones, a central flowzone and an outer flow zone. The compositions and flow rates of theprocess gases used in the central flow zone and the outer flow zone maybe varied and controlled independently from one another. Controlling therespective flow rates of process gases used in the central and outerflow zones affects the radial flow distribution of gases over thesubstrate and the film thickness uniformity. Flow dynamics of theprocess gas that passes over the substrate critically impacts theuniformity of the deposited film. A system controller (not shown) may beused to control various operating parameters associated with thereaction chamber 102 including, for example, process gas flow rates andcompositions and reaction chamber temperature and pressure. The processgas may also be introduced into the reaction chamber according to othergas manifold configurations.

FIG. 3 illustrates the gas manifold 140 with the injection port liner141 not shown for illustration. The injector baffle plate 145 includes abody 146, a first end 147, second end 148, front and rear opposing faces149, 150, and an array 151 of holes 152, 153 within the body 146extending between faces 149, 150 for distributing gases from theinjection port liner 141 to the inject insert liner assembly 170. Thebody 146 of injector baffle plate 145 may be formed of quartz to reducecontamination within the reaction chamber 102, although other materialsmay also be suitable for the body 146, including passivated stainlesssteel (e.g., stainless steel grade 316L), silicon carbide, or any othermaterial that enables the gas manifold 140 to function as describedherein.

The array 151 of holes 152, 153 may be arranged along a singular axisextending in a widthwise direction Y of the system 100, although otherarrangements are possible, such as a stacked configuration, where two ormore holes are arranged above and below one another, a staggeredconfiguration, where the holes are arranged along two or more parallelaxes in an alternating pattern, a slantwise configuration, where theholes are arranged along two or more intersecting axes in an alternatingpattern, and any combination thereof. The array 151 may include innerand outer arrays 154, 155 of holes 152, 153 characterized by referenceto a midpoint M1 midway between the first end 147 and the second end 148of the baffle plate 145, as shown in FIG. 4. Specifically, the innerarray 154 may include one or more holes 152 disposed within a certaindistance from midpoint M1 or within a certain number of holes frommidpoint M1 (e.g., within 6 holes from the midpoint M1), and the outerarray 155 may include one or more holes 153 disposed within a certaindistance from either the first end 147 or the second end 148, or withina certain number of holes from the first end 147 or second end 148(e.g., within holes from the first end 147 or second end 148). In theembodiment shown in FIG. 4, the inner array 154 includes 12 holes 152,disposed within 6 holes on either side of midpoint M1, and the outerarray 155 includes 10 holes 153, disposed within 5 holes of either thefirst end 147 or the second end 148. In certain embodiments, some holes(not shown) in the array 151 may not be included in either the innerarray 154 or the outer array 155.

The number, size and cross-sectional shape of holes 152, 153 withinbaffle plate 145 may vary. In some embodiments, the baffle plate 145 mayinclude between 14 and 30 holes, between 16 and 28 holes, between 18 and26 holes, or between 20 and 24 holes, although the baffle plate 145 mayinclude any other suitable number of holes 152, 153 that allows the gasmanifold 140 to function as described herein. In some embodiments, suchas the embodiment shown in FIG. 4, one or more holes 152, 153 may have acircular cross-section, wherein the size of such holes 152, 153 ischaracterized by an outer diameter D of the hole. In some embodiments,one or more holes may have a polygonal cross-section (e.g., square,rectangular, hexagonal, etc.), wherein the size of such holes ischaracterized by the distance between opposing faces of the polygon (inthe case of a polygon with an even number of sides) or the distancebetween an opposing face and corner of the polygon (in the case of apolygon with an odd number of sides). In some embodiments, one or moreholes may have a rectangular cross-section or an ellipticalcross-section (e.g., an elongated slit), wherein the size of such holesis characterized by the length of the major axis of the rectangle orellipse, and the length of the minor axis of the rectangle or ellipse.In yet other embodiments, one or more holes may have any other suitableshape that allows the gas manifold 140 to function as described herein.In some embodiments, holes having a circular cross-section may have adiameter between about 3 millimeters and about 12 millimeters, betweenabout 6 millimeters and about 10 millimeters, or between about 7millimeters and about 9 millimeters. In some embodiments, holes having apolygonal cross-section may have a size between about 3 millimeters andabout 12 millimeters, between about 6 millimeters and about 10millimeters, or between about 7 millimeters and about 9 millimeters. Inthe embodiment shown in FIG. 4, the baffle plate 145 includes 22 holes152, 153 each having a circular cross-section with a diameter D of about8 millimeters.

The injector baffle plate 145 may also include one or more locks 156 forsecuring one or more plugs 160, 163 (shown in FIG. 5) to the injectorbaffle plate 145. The lock 156 may comprise any means suitable forsecuring one or more plugs 160, 163 to the injector baffle plate 145,including counter-sunk shoulders, set screws, pins, slots, threads, andeven adhesives. In some embodiments, a single lock may be configured tosecure more than one plug 160, 163 to the baffle plate 145. The lock 156may be disposed within one of the holes 152, 153 in the baffle plate145, or the lock may be disposed outside the holes. In the embodimentshown in FIG. 4, each hole 152, 153 includes a lock 156 comprising acounter-sunk shoulder extending inwardly from the inner surface of therespective hole. Each counter-sunk shoulder is sized to prevent thepassage of a plug 160, 163 (shown in FIG. 5) therethrough. Thecounter-sunk shoulder may extend inwardly from the inner surface of ahole any distance suitable to prevent the passage of a plugtherethrough, and to permit the passage of gas therethrough when anorifice-containing plug 160 (shown in FIG. 5) is disposed therein. Insome embodiments, one or more counter-sunk shoulders may extend inwardlybetween about 0.5 millimeters and about 1.5 millimeters. The depth atwhich the counter-sunk shoulders are disposed in a given hole may varydepending on the thickness of a plug to be received within the hole. Insome embodiments, one or more counter-sunk shoulders may be disposedwithin a hole at a depth of between about 3 millimeters and about 8millimeters, between about 4 millimeters and about 7 millimeters, orbetween about 5 millimeters and about 6 millimeters. In the embodimentshown in FIG. 4, each hole 152, 153 includes a lock 156 comprising acounter-sunk shoulder extending inwardly a distance of about 1millimeter from the inner surface of the hole, and disposed at a depthof about 5.4 millimeters.

Referring now to FIG. 5, one or more plugs 160, 163 each sized to bereceived within one or more of the holes 152, 153 may be provided tocontrol the gas flow distribution across the substrate surface 116within the reaction chamber 102. The plugs 160, 163 may be formed ofquartz, although other materials may also be suitable for the plugs 160,163, including passivated stainless steel (e.g., stainless steel grade316L), silicon carbide, or any other material that enables the gasmanifold 140 to function as described herein. In some embodiments, oneor more of the plugs 160 may include an orifice 161 therethrough topermit the passage of gas. In some embodiments, one or more of the plugs163 may be solid with no orifice therethrough to restrict the passage ofgas. The baffle plate 145 and plugs 160, 163 aid the operator (notshown) of the CVD system in controlling the gas flow distribution acrossthe substrate surface 116 by permitting the size of the holes 152, 153within baffle plate 145 to be easily adjusted by inserting or removing aselected plug from a selected hole. The baffle plate 145 and plugs 160,163 thus provide the operator with the ability to selectively adjust thegas flow distribution across the substrate surface. In some embodiments,one or more plugs 160, 163 may be capable of being removably secured tothe baffle plate 145 within one of the holes 152, 153 (e.g., by acounter-sunk shoulder within baffle plate 145), thereby facilitating theability to adjust and control the gas flow distribution across thesubstrate surface 116.

Each plug 160, 163 includes a body 162 sized to be received within oneor more of the holes 152, 153 in the baffle plate 145. The size andcross-sectional shape of each plug may vary. In some embodiments, one ormore plugs may include a generally cylindrical body, such as the plug160 shown in FIG. 5, wherein the size of such plugs is characterized bythe outer diameter of the body d_(p). In some embodiments, one or moreplugs may include a polygonal body, such as the plug 260 shown in FIG.6, wherein the size of such plugs is characterized by the distance d_(p)between opposing faces of the polygon (in the case of a polygon with aneven number of sides) or the distance between an opposing face andcorner of the polygon (in the case of a polygon with an odd number ofsides). In some embodiments, one or more plugs may include a generallyrectangular body or a generally elliptical body, wherein the size ofsuch plugs is characterized by the length of the major axis of therectangle or ellipse, and the length of the minor axis of the rectangleor ellipse. In yet other embodiments, one or more plugs may have anyother suitable shape that allows the gas manifold 140 to function asdescribed herein. In some embodiments, one or more plugs may have a sizebetween about between about 3 millimeters and about 12 millimeters,between about 6 millimeters and about millimeters, or between about 7millimeters and about 9 millimeters. In the embodiment shown in FIG. 5,each plug 160, 163 includes a generally cylindrical body 162 having anouter diameter d_(p) of about 8 millimeters.

Referring to FIG. 7, in yet other embodiments, one or more plugs 360 mayinclude a plug extension portion 363 having a size d_(e) different thanthe primary size d_(p) of the plug body 362. Orifice-containing plugs,such as the orifice containing-plug 361 shown in FIG. 7, as well assolid plugs with no orifice therein, such as the plug 163 shown in FIG.5, may include a plug extension portion 363. In some embodiments, one ormore plug extension portions 363 may be sized to be received within alock 156 within a baffle plate hole 152, 153. In some embodiments, oneor more plug extension portions 363 may be sized to be received within acounter-sunk shoulder. In the embodiment shown in FIG. 7, the plugextension portion 363 is sized to be received within a counter-sunkshoulder. In the embodiment shown in FIG. 7, the plug extension portion363 has a size d_(e) of about 7.0 millimeters, and plug body 362 has aprimary size d_(p) of about 8.0 millimeters.

Each orifice 161 extending through each orifice-containing plug, such asthe orifice-containing plug 160 shown in FIG. 5, has a cross-sectionalshape. The size and cross-sectional shape of orifices 161 in differentorifice-containing plugs 160 may vary. In some embodiments, one or moreorifices 161 in one or more orifice-containing plugs 160 may comprise acircular aperture, such as the orifice 161 shown in FIG. 5, wherein thesize of such apertures is characterized by the inner diameter d_(o) ofsuch apertures. In some embodiments, one or more orifices 161 in one ormore orifice-containing plugs 260 may comprise a polygonalcross-section, such as the orifice 261 shown in FIG. 6, wherein the sizeof such orifices is characterized by the distance d_(o) between opposingfaces of the polygon (in the case of a polygon with an even number ofsides) or the distance between an opposing face and corner of thepolygon (in the case of a polygon with an odd number of sides). In someembodiments, one or more orifices in one or more orifice-containingplugs may include a generally elliptical cross-section, wherein the sizeof such orifices is characterized by the length of the major axis of theellipse. In yet other embodiments, one or more orifices may have anyother suitably shaped cross-section that allows the gas manifold 140 tofunction as described herein. In some embodiments, one or more orificeshaving a circular cross-section may have an inner diameter between about1 millimeter and about 7 millimeters, between about 2 millimeters andabout 6 millimeters, or between about 2 millimeters and about 5millimeters. In some embodiments, one or more orifices may have a sizebetween about millimeter and about 7 millimeters, between about 2millimeters and about 6 millimeters, or between about 2 millimeters andabout 5 millimeters.

Any combination of plugs having any combination of size, body shape,orifice shape, and orifice size may be used in a single embodiment.Because the plugs may be removably secured to the baffle plate, theeffective size of each baffle plate hole can easily be adjusted by usingdifferent plug combinations with the baffle plate. As a result, the gasflow distribution across the substrate surface may be selectivelyadjusted, and more uniform growth rates can be achieved in chemicalvapor deposition systems employing the gas manifolds described herein.

In certain embodiments, the size, body shape, orifice shape, and orificesize of the plugs 160, 163 may vary depending upon the position of theplug 160, 163 within the array of holes. For example, referring to theembodiment shown in FIGS. 8-10, a plurality of plugs 160, 163 aredisposed within the array 151 of holes 152, 153 in the baffle plate 145.The array 151 of holes 152, 153 includes an inner array 154 of holes 152and an outer array 155 of holes 153. Several of the plugs 160 includeorifices 161, wherein each orifice 161 comprises a circular aperturehaving a diameter d_(o). In other embodiments, the orifices may havepolygonal cross-sections, elliptical cross-sections, or any othersuitably shaped cross-section that allows the gas manifold 140 tofunction as described herein. Referring again to FIGS. 8-10, eachaperture-containing plug 160 disposed in the inner array 154 has anaperture diameter d_(o) between about millimeters and about 6millimeters. In other embodiments, each aperture-containing plug 160disposed in the inner array 154 may have an aperture diameter d_(p)between about 4 millimeters and about 5 millimeters. In the embodimentshown in FIGS. 8-10, at least one plug 163 disposed in the outer array155 of holes 153 is solid with no holes therein. In other embodiments,each plug disposed in the outer array has an orifice therethrough. Inthe embodiment shown in FIGS. 8-10, the aperture-containing plugs 160disposed in the outer array 155 each have an aperture diameter d_(p)between about 1 millimeter and 6 millimeters. In other embodiments, eachaperture-containing plug 160 disposed in the outer array 155 has anaperture diameter d_(p) between about 2 millimeters and about 5millimeters.

Referring now to FIGS. 11-12, the gas manifold 140 of FIG. 3 is shownwith the baffle plate 145 not shown for illustration. As discussedabove, the inject insert liner assembly 170 may be a single or unitaryinsert, or it may be formed from separate inserts, including, forexample, a first inject insert 170L and a second inject insert 170R. Insome embodiments, the first inject insert 170L and second inject insert170R may each be further divided into separate components, includingupper halves 170La, 170Ra and lower halves 170Lb, 170Rb, as shown inFIGS. 13-14. Inject inserts comprising separate components makesfabricating the gas flow channels therein (described below) easier thaninject inserts comprising a unitary construction. Whereas features ofthe first inject insert 170L and the second inject insert 170R aredescribed in more detail below, it should be understood that a unitaryinsert may include any one or more of these features. The inject inserts170L, 170R may be fabricated from quartz or, more specifically,transparent quartz, although other materials may also be suitable,including passivated stainless steel (e.g., stainless steel grade 316L),silicon carbide, or any other material that enables the gas manifold 140to function as described herein.

Each inject insert 170L, 170R includes a plurality of gas flow channels172-182 defined therein disposed along a widthwise or horizontaldirection Y of the system 100, each extending in a lengthwise directionZ of the system 100. The flow channels 172-182 provide fluidcommunication between the gas injection port 106 and the processingchamber 102. Each flow channel 172-182 is defined by four surfaceswithin each inject insert 170L, 170R. The surfaces defining a given flowchannel may vary depending on whether the flow channel is an interiorflow channel 173-181 or an exterior flow channel 172, 182. Interior flowchannels 173-181 may be defined by an upper surface 183L, 183R of theinject inserts 170L, 170R, a lower surface 184L, 184R of the injectinsert 170L, 170R, and the surfaces of neighboring partition walls 185.Exterior flow channels 172, 182 may be defined by the upper surface183L, 183R of the inject insert 170L, 170R, the lower surface 184L, 184Rof the inject insert 170L, 170R, a surface of a partition wall 185, andone of the outer peripheral surfaces 186L, 186R of the inject insert170L, 170R. The partition walls 185 shown in FIGS. 11-12 extendvertically between the upper and lower surfaces 183, 184 of each injectinsert 170L, 170R, and extend the length of the inject insert 170L, 170Rin a lengthwise direction Z of the system 100.

Each flow channel 172-182 includes an inlet 187 adjacent to the baffleplate 145, and an outlet 188 downstream from the inlet 187. The inlet187 may be disposed on the front surface 189L, 189R of the inject insert170L, 170R, and the outlet 188 may be disposed on the rear surface 190L,190R of the inject insert 170L, 170R. The cross-sectional shape of eachinlet 187 may be square, circular, elliptical, rectangular, polygonal,or any other suitable shape that allows the gas manifold 140 to functionas described herein. The cross-sectional shape of each outlet 188 mayalso be square, circular, elliptical, rectangular, polygonal, or anyother suitable shape that allows the gas manifold 140 to function asdescribed herein. The outlet corresponding to a given inlet may have thesame cross-sectional shape as the inlet, or the outlet may have adifferent cross-sectional shape than the corresponding inlet. In theembodiment shown in FIGS. 11-12, the cross-sectional shape of each inlet187 is square, the cross-sectional shape of each outlet 188corresponding to an interior flow channel 173-181 is rectangular, andthe cross-sectional shape of each outlet 188 corresponding to anexterior flow channel 172, 182 is partially square and partiallyrounded.

The cross-sectional area of each inlet 187 may be any size suitable toallow the gas manifold 140 to function as described herein. In someembodiments, the cross-sectional area of one or more inlets 187 may besized based upon the size of one or more holes in the baffle plate. Forexample, in embodiments where one or more flow channels 172-182 eachcorrespond to a single hole in the baffle plate (described below), thecross-sectional area of one or more inlets 187 may be less than about 10times the cross-sectional area of the corresponding baffle plate hole,less than about 5 times the cross-sectional area of the correspondingbaffle plate hole, or less than about 3 times the cross-sectional areaof the corresponding baffle plate hole. In embodiments where the baffleplate contains one or more orifice containing plugs, such as theorifice-containing plug 160 shown in FIG. 5, the cross-sectional area ofone or more inlets 187 may be sized based upon the size of one or moreorifices in the orifice-containing plugs disposed in the baffle plate.For example, in embodiments where one or more flow channels 172-182 eachcorrespond to a single hole in the baffle plate (described below), andone or more holes in the baffle plate contains an orifice containingplug therein, the cross-sectional area of one or more inlets 187 may beless than about 5 times the cross-sectional area of the orifice in anorifice-containing plug, less than about 3 times the cross-sectionalarea of the orifice in an orifice-containing plug, or less than about1.5 times the cross-sectional area of the orifice in anorifice-containing plug. In the embodiment shown in FIGS. 11-12, thecross-sectional area of each inlet 187 is less than about 1.5 times thecross-sectional area of the largest orifice 161 in theorifice-containing plugs 160 disposed in the baffle plate 145. In someembodiments, the cross-sectional area of one or more inlets 187 may besized based upon the cross-sectional area of the outlet 188corresponding to that inlet. In particular, one or more inlets 187 maybe sized such that the cross-sectional area of the inlet is less thanthe cross-sectional area of the outlet corresponding to that inlet.

The front surface 189L, 189R of each inject insert 170L, 170R isgenerally planar and sits substantially flush with the baffle plate 145when disposed within the system 100. The rear surface 190L, 190R of eachinject insert 170L, 170R may be curved inwardly to match the contours ofthe upper and lower liners 134, 136, as shown in FIGS. 2 and 11-12. Insome embodiments, the front surface of an inject insert may be adjoinedto the baffle plate such that the baffle plate and the inject insertcomprise a unitary member.

The number of flow channels 172-182 defined within the inject insertliner assembly 170 may vary in different embodiments. In someembodiments, the total number of flow channels defined by the injectinsert liner assembly 170 may be between 16 and 28, between 18 and 26,or between 20 and 24, although the total number of flow channels may beany other suitable number that allows the gas manifold 140 to functionas described herein. In the embodiment shown in FIGS. 11-12, the injectinsert liner assembly 170 includes a total of 22 gas flow channels172-182, with each inject insert 170L, 170R having 11 flow channelstherein. In some embodiments, the number of flow channels 172-182defined by the inject insert liner assembly 170 may correspond to thenumber of holes in baffle plate 145. In some embodiments, there may be aone-to-one correspondence between the number of holes in baffle plate145 and the number of flow channels 172-182 defined by the inject insertliner assembly 170. In other embodiments, the correspondence may differ,such as a two-to-one correspondence (i.e., two holes for every one flowchannel), a three-to-one correspondence, a four-to-one correspondence,or a five-to-one correspondence. In the embodiment shown in FIGS. 11-12,there is a one-to-one correspondence between the number of flow channels172-182 and the number of holes 152, 153 in baffle plate 145.Specifically, the baffle plate 145 includes a total of 22 holes 152,153, and the inject insert liner assembly 170 includes a total of 22flow channels 172-182, wherein each of the first and second injectinserts 170L, 170R include 11 flow channels 172-182. Each flow channel172-182 shown in FIGS. 11-12 corresponds to a single hole 152, 153 inthe baffle plate 145 than the other flow channels. CVD systems having aone-to-one correspondence between the number of flow channels and thenumber of holes in the baffle plate reduces the negative effectsassociated with “crosstalk” between inner and outer flow zones in thegas manifold, namely, unpredictable tuning responses from adjusting thegas flow rates in the inner and outer flow zones. Additionally, theone-to-one correspondence between the number of flow channels and thenumber of holes in the baffle plate reduces the negative effectsassociated with having multiple baffle plate holes in fluidcommunication with a single inject insert flow channel, namely, theformation of recirculation cells within the inject insert linerassembly.

As shown in FIGS. 11-12, one or more flow channels 172-182 definedwithin the inject inserts 170L, 170R may be tapered along the lengthwisedirection Z of the system 100 in at least one of a vertical (i.e., alongthe X axis) or horizontal (i.e., along the Y axis) direction. In someembodiments, one or more flow channels may be tapered outwardly in thehorizontal direction from the flow channel inlet 187 to the flow channeloutlet 188, such as the flow channels 172-182 shown in FIGS. 11-12. Insome embodiments, one or more flow channels may be tapered outwardly inthe vertical direction from the flow channel inlet 187 to the flowchannel outlet 188, such as the flow channels 172-182 shown in FIGS.11-12. In some embodiments, one or more flow channels may be taperedoutwardly in both the vertical and horizontal directions from the flowchannel inlet 187 to the flow channel outlet 188, such as the flowchannels 172-182 shown in FIGS. 11-12. In some embodiments, one or moreflow channels may be tapered inwardly in the vertical direction from theflow channel inlet 187 to the flow channel outlet 188.

The degree of taper in each flow channel 172-182 may vary in differentembodiments. In some embodiments, one or more flow channels taperedoutwardly in the horizontal direction may be tapered at an angle ofbetween about 1 degree and about 15 degrees, between about 2 degrees andabout 10 degrees, or between about 2 degrees and about 7 degrees,wherein the angle of such taper is measured with respect to thelengthwise direction Z of the system 100. In some embodiments, one ormore flow channels tapered outwardly in the vertical direction may betapered at an angle of between about 1 degrees and about 15 degrees,between about 2 degrees and about 10 degrees, or between about 2 degreesand about 7 degrees, wherein the angle of such taper is measured withrespect to the lengthwise direction Z of the system 100. In someembodiments, the degree of taper in the horizontal and/or the verticaldirection of one or more flow channels may be selected such that thesize of the inlets and outlets of the flow channels correspond to thesize of the baffle plate holes and the openings formed between the upperand lower liners (shown at 134 and 136 in FIG. 1). In this way, theinject insert liner assemblies described herein can be integrated in CVDsystems already in use, and the benefits of such inserts can be realizedwith little or no modification of existing CVD systems. In someembodiments, the degree of taper in the horizontal and/or the verticaldirection of one or more flow channels may be selected such that thesize of the inlets correspond to the size of an orifice in anorifice-containing plug disposed in a baffle plate hole, and the size ofthe outlets correspond to the openings formed between the upper andlower liners (shown at 134 and 136 in FIG. 1). In this way, the injectinsert liner assemblies described herein can be integrated in CVDsystems employing the novel baffle plate and plugs described herein, andthe benefits of such inserts can be realized with little or nomodification of such CVD systems.

In the embodiment shown in FIGS. 11-12, the degree of taper in thehorizontal and vertical direction of each flow channel 172-182 isselected such that the size of each inlet 187 corresponds to the size ofa respective baffle plate hole 152, 153 (i.e., the baffle plate hole influid communication with the flow channel), and the size of each outlet188 corresponds to the openings formed between the upper and lowerliners 134, 136. Because the length of each flow channel 172-182 variesin the lengthwise direction Z, the degree of taper in the horizontal andvertical direction of each flow channel 172-182 also varies. Forexample, flow channels having a shorter length, such as flow channels172-177, will have higher degrees of taper, such as between about 2degrees and about 15 degrees in the vertical direction, and betweenabout 2 degrees and 15 degrees in the horizontal direction. Flowchannels having a longer length, such as flow channels 178-182, willhave a lower degree of taper, such as between about 1 degree and about10 degrees in the vertical direction, and between about 1 degree and 10degrees in the horizontal direction. Inject inserts having graduallytapered flow channels from the inlet side to the outlet side, such asinject inserts 170L and 170R, further help prevent the formation ofrecirculation cells within the inject insert by preventing rapidexpansion of the process gas 110 as it flows through the differentcomponents of the gas manifold.

In operation, gas is introduced into the CVD system from the gasinjecting port at a selected flow rate. The gas manifold 140 is providedwithin the CVD system 100 to direct incoming gas 110 into the processingchamber 102. The gas manifold 140 may be disposed between the gasinjecting port 106 and processing chamber 102. In embodiments where thegas manifold 140 includes an injection port liner 141, the gas manifold140 may extend into the gas injection port 106, as shown in FIG. 1. Thegas manifold 140 may be provided with the novel baffle plate 145 andplugs 160, 163, and the novel inject insert liner assembly 170 describedherein, or the gas manifold 140 may be provided with the novel baffleplate 145 and plugs 160, 163 described herein in combination with aconventional inject insert, or the gas manifold may be provided with aconventional baffle plate in combination with the novel inject insertliner assembly 170 described herein.

In CVD systems including the novel baffle plate 145 and plugs 160, 163described herein, the gas flow distribution across the substrate surfacemay be controlled by varying the effective size of the holes 152, 153 inthe baffle plate 145. For example, one or more plugs 160 having anorifice 161 may be selected to be inserted within one or more holes 152,153 in the baffle plate 145. Plugs 160 having different orifice sizesmay be selected such that the effective size of the baffle plate holesvaries across the length of the baffle plate 145. By varying theeffective size of the baffle plate holes 152, 153, the gas flow rate atdifferent regions on the substrate surface can be selectively adjusted,thus providing the operator of the CVD system the ability to moreselectively control the gas flow distribution across the substratesurface compared to conventional CVD systems.

In some embodiments, the orifice 161 in each orifice-containing plug 160selected to be inserted into a hole 152, 153 in baffle plate 145comprises a circular aperture having a diameter d_(o). The plugs 160selected to be inserted into the inner array 154 of holes 152 may varyfrom the plugs 160 selected to be received in the outer array 155 ofholes 153. For example, the orifice-containing plugs 160 selected forthe inner array 154 of holes 152 may have aperture diameters betweenabout millimeters and about 6 millimeters, or between about 4millimeters and about 5 millimeters. The orifice-containing plugs 160selected for the outer array 155 of holes 153 may have aperturediameters between about 1 millimeter and about 6 millimeters, or betweenabout 2 millimeters and about 5 millimeters.

In some embodiments, at least one plug selected to be inserted into theouter array 155 of holes 153 is a solid plug 163 with no holes therein.In some embodiments, each plug selected to be inserted into the outerarray 155 of holes 153 is an orifice-containing plug 160. In someembodiments, at least one plug selected to be inserted into the innerarray 154 of holes 152 is a solid plug 163 with no holes therein. Insome embodiments, each plug selected to be inserted into the inner array154 of holes 152 is an orifice-containing plug 160.

In CVD systems including the novel baffle plate 145 and plugs 160, 163and/or the novel inject insert liner assembly 170 described herein, theuniformity of the gas flow distribution across the substrate surface canbe maintained at higher gas flow rates than in conventional CVD systems.For example, process gas, such as a tricholorsilane-hydrogen mixture,may be introduced into the CVD system at a flow rate of at least about15 standard-liters per minute, at least about 17 standard-liters perminute, or even at least about 19 standard-liters per minute, whilemaintaining a relative layer thickness variation of less than about 4%across the substrate surface, less than about 2% across the substratesurface, or even less than about 1% across the substrate surface.Carrier gas, such as hydrogen, may also be introduced at a higher flowrate, such as at least about 70 standard-liters per minute, at leastabout standard-liters per minute, or even at least about 90standard-liters per minute, while maintaining a relative layer thicknessvariation of less than about 4% across the substrate surface, less thanabout 2% across the substrate surface, or even less than about 1% acrossthe substrate surface. Because the uniformity of the gas flowdistribution across the substrate surface can be maintained at highergas flow rates, the rate at which a given film or layer is deposited ona substrate may also be increased while maintaining uniformity in thelayer thickness. For example, an epitaxial layer may be deposited on asilicon wafer having a diameter of at least about 150 millimeters, atleast about 200 millimeters, at least about 300 millimeters, or even atleast about 450 millimeters at a deposition rate of at least about 2.3micrometers per minute, at least about 2.5 micrometers per minute, oreven at least about 2.7 micrometers per minute while maintaining arelative layer thickness variation of less than about 4% across thediameter of the wafer, less than about 2% across the diameter of thewafer, or even less than about 1% across the diameter of the wafer.

“Relative layer thickness variation” of a deposited layer is determinedby measuring the difference between the maximum layer thickness and theminimum layer thickness, and dividing this difference by the averagelayer thickness. The resultant value is multiplied by 100 in order toarrive at a percentage. This percentage is the “relative layer thicknessvariation” as disclosed herein. As used herein, the term“standard-liter” refers to one liter of the referenced gas at 0° C. and101.3 kPa (1013 millibar).

The embodiments described herein are suited for processing semiconductoror solar-grade wafers, though may be used in other applications. Theembodiments described herein are particularly suited for use inatmospheric-pressure silicon on silicon chemical vapor depositionepitaxy using gas mixtures including hydrogen, tricholorosilane, anddiborane. Silicon precursors other than tricholorosilane may also beused with the embodiments described herein, including dichlorosilane,silane, trisilane, tetrachlorosilane, methylsilane, pentasilane,neopentasilane, and other higher order silane precursors. Precursorsother than silicon precursors may also be used with the embodimentsdescribed herein, including germane, digermane, and other germaniumprecursors. Dopant gas species other than diborane may be used,including phosphine and arsine. The embodiments described herein mayalso be used in processes other than atmospheric-pressure silicon onsilicon epitaxy, including reduced-pressure epitaxy (e.g., at pressuresbetween about 10 Torr and about 750 Torr), silicon-germanium epitaxy,carbon-doped silicon epitaxy, and non-epitaxial chemical vapordeposition. The embodiments described herein may also be used to processwafers other than silicon wafers, including germanium wafers, galliumarsenide wafers, indium phosphide wafers, and silicon carbide wafers.

As described above, gas manifolds including the novel baffle plates andplugs and/or the novel inject insert liner assemblies of the presentdisclosure provide an improvement over known gas manifolds. The baffleplates and plugs provide the operator of the CVD system the ability toselectively adjust the gas flow distribution across the substratesurface within the processing chamber. As a result, uniformity in gasflow distribution across the substrate surface can be improved,particularly at higher gas flow rates. The inject insert linerassemblies described herein reduce the negative effects associated withcrosstalk between multiple flow zones feeding into a single injectinsert channel, namely unpredictable tuning responses. These negativeeffects are avoided by providing, among other things, a one-to-onecorrespondence between the number of baffle plate holes and the totalnumber of gas flow channels within the inject insert liner assembly.Additionally, the inject insert liner assemblies described herein reducethe negative effects associated with the formation of recirculationcells, namely, degradation in the uniformity of the gas flowdistribution within the processing chamber. These negative effects areavoided by providing inject insert liner assemblies having gas flowchannels that are gradually tapered along a lengthwise direction of theCVD system.

When introducing elements of the present invention or the embodiment(s)thereof, the articles “a”, “an”, “the” and “said” are intended to meanthat there are one or more of the elements. The terms “comprising”,“including” and “having” are intended to be inclusive and mean thatthere may be additional elements other than the listed elements.

As various changes could be made in the above constructions and methodswithout departing from the scope of the invention, it is intended thatall matter contained in the above description and shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

What is claimed is:
 1. A system for depositing a layer on a substrate,the system comprising: a processing chamber; a gas injecting port forintroducing gas into the system, the gas injecting port disposedupstream from the processing chamber; and a gas distribution platedisposed between the gas injecting port and the processing chamber, thegas distribution plate including: an elongate planar body and an arrayof holes therein, and a plug sized to be received within one of theholes, the plug having an orifice therethrough for permitting thepassage of gas, wherein the plug is capable of being removably securedto the gas distribution plate within one of the holes.
 2. The system asset forth in claim 1 further comprising a lock for securing the plug tothe gas distribution plate.
 3. The system as set forth in claim 2wherein the lock includes a countersunk shoulder extending inwardly froman inner surface of one of the holes, the countersunk shoulder beingsized to prevent the passage of a plug through the hole.
 4. The systemas set forth in claim 2 wherein the plug includes a plug extensionportion sized to be received within the lock.
 5. The system as set forthin claim 1 wherein the plug includes a generally cylindrical body havingan outer diameter sized to be received within one of the holes in thegas distribution plate.
 6. The system as set forth in claim 1 whereinthe plug includes a polygonal body sized to be received within one ofthe holes in the gas distribution plate.
 7. The system as set forth inclaim 1 wherein the orifice in the plug includes a circular aperturehaving a diameter.
 8. The system as set forth in claim 7 wherein thediameter of the aperture in the plug is between about 1 millimeter andabout 6 millimeters.
 9. The system as set forth in claim 1 wherein theorifice in the plug includes a polygonal cross section.
 10. The systemas set forth in claim 1 wherein the plug is one of a plurality of plugseach sized to be received within one of the holes and capable of beingremovably secured to the gas distribution plate.
 11. The system as setforth in claim 10 wherein at least one of the plugs is solid with noholes therein.
 12. The system as set forth in claim 10 wherein at leastone of the plugs includes a circular aperture having a diameter.
 13. Thesystem as set forth in claim 12 wherein at least one plug is disposed inthe array of holes, and wherein the array of holes includes an innerarray of holes and an outer array of holes, and each aperture-containingplug disposed in the inner array has an aperture diameter between about3 millimeters and about 6 millimeters, and each aperture-containing plugdisposed in the outer array has an aperture diameter between about 1millimeter and about 6 millimeters.
 14. The system as set forth in claim13 wherein at least one plug disposed in the outer array is solid withno holes therein.
 15. The system as set forth in claim 13 wherein theinner array of holes includes between 10 and 14 holes and the outerarray of holes includes between 8 and 12 holes.
 16. The system as setforth in claim 10 wherein two or more plugs are coupled together. 17.The system as set forth in claim 1 wherein at least one hole has apolygonal cross section.
 18. A method of depositing a layer on asubstrate disposed within a processing chamber within a depositionsystem, the method comprising the steps of: introducing a process gasinto the system from a gas injecting port, the gas injecting portdisposed upstream from the processing chamber; flowing the process gasthrough a gas distribution plate in fluid communication with the gasinjecting port and the processing chamber, the gas distribution plateincluding an inner array of holes and an outer array of holes; andcontrolling the gas flow distribution across the substrate surface, thecontrolling step including selecting at least one orifice-containingplug to be secured within a hole in the gas distribution plate, andsecuring the selected plug within the hole.
 19. The method as set forthin claim 18 wherein the process gas includes a gas selected from thegroup consisting of tricholorosilane, dichlorosilane, silane, trisilane,tetrachlorosilane, methylsilane, pentasilane, and neopentasilane. 20.The method as set forth in claim 18 wherein the process gas includes agas selected from the group consisting of germane and digermane.
 21. Themethod as set forth in claim 18 further comprising depositing a layer onthe substrate.
 22. The method as set forth in claim 21 wherein thesubstrate is a silicon wafer, a germanium wafer, a gallium arsenidewafer, an indium phosphide wafer, or a silicon carbide wafer.
 23. Themethod as set forth in claim 21 wherein the layer is an epitaxial layer.